System of operation of a steam-gas circuit or of a gas circuit for gas turbines comprising a combustion chamber for solid fuel



United States Patent O SYSTEM F QPERATION 0F A 'STEAM-GAS CIR- CUIT 0R0F A GAS CIRCUIT FOR G'AS TUR- BENES 'COMPRISIN G A COMBUSTION CHAMBERFOR SOLID FUEL Ladisiav Michalika, 8 Amurska, Prague 10, Czechoslovakia,and Bohuslav Limpouch, '1214 Pushkinova, Hradec Kralove, CzechoslovakiaFiled `luly 31, 1962, Ser. No. 216,717 10 Claims. (Cl. 60-39.02)

This invention relates to an improved operating system of a steam-gas orgas circuit of gas turbines with a combustion chamber for solid fuel,where the combustion products at elevated pressure are separated afterburning from the solid remnants of burning, whereas they are atadmission temperature and pressure supplied as driving gases into thegas turbine, where they expand and render mechanical energy.

There have been repeated attempts to use solid fuel for the gas turbinecircuits. Proposals have been made for instance to burn coal at elevatedpressure in a heating chamber and to use a direct passage of thecombustion products through the turbine. A substantial drawback, whichhas not yet been removed is the separation of solid remnants from thecombustion products, which remnants cause erosion of the turbine bladesor form deposits in the turbine.

Other proposed solutions rely on the heating7 of clean compressed airprior to the entrance into the turbine by means of a high temperatureheat exchanger heated by coal combustion products at approximatelyatmospheric pressure. As combustion air hot air leaving the turbineafter expansion is used. A drawback of this solution is the need of alarge and expensive heat exchanger made of alloyed material. A furtherproposed solution is the gasifying of coal under pressure, cleaning ofthe gas and its burning in a combustion chamber of the gas turbine. Adrawback of this system is however the complexity of the arrangement, aworse eiectiveness namely of the gas generator and its relatively smalloutput.

The said drawbacks cause that solid fuel is used for the drive of gasturbines only in sporadic cases. The same holds true about steam-gasdevices.

It is commonly known that it is possible to achieve at steam-gas cyclesa better thermal effect and in addition, namely for cycles with steamgenerators heated at elevated pressures, also a reduction of the sizeand weight of the steam generator. At increased pressure of thecombustion products the heat transmission coefcient from the combustionproducts to the wall increases, so that the required heat transmittingsurface is reduced. The hot compressed combustion products expand afterleaving the combustion chamber of the steam generator in the gasturbine. The actual drawback is however, that solid fuel cannot be usedin this case due to the above mentioned difficulties with the separationof solid remnants from the combustion products. v

It is an object of this invention to eliminate this drawback. Inaccordance with this invention, solid fuel is burnt at elevated pressureand the hot compressed combustion products expand in the gas turbine,but contrary to presently known arrangements of this kind the separationof the solid remnants after burning from the stream of combustionproducts takes place at a lower temperature than the supply temperatureof the combustion products into the gas turbine. As the removal of dustis substantially easier and more effective at low temperature, it ispossible to achieve in accordance with this invention the requireddegree of purity of the combustion products.

The cooling of the compressed combustion products in order to ease theremoval of dust is carried out in a 3,2%,175 Patented Aug. 31, 1965system of two or more heat exchangers arranged in the stream of notcleaned combustion products, the first of which heat exchangers,arranged behind the pressure combustion chamber, serves for thereheating of the driving gases, i.e. of the cleaned compressedcombustion products, to the admission temperature of the gas turbine,while the following one or more heat exchangers serve for other purposesof the cycle as heating device of the advantageously regenerating type,serving for heating the compressed combustion air, supplied by acompressor to the combustion chamber, or eventually also as an auxiliaryeconomiser, serving for preheating the supply water or the condensatefor the steam generator, or further coolers serving other technologicalpurposes of the cycle and similar.

In accordance with the invention the injection of suitably preparedwater into the stream of combustion products is used prior or aftertheir cleaning from dust or prior and after their cleaning, or in casethe separation of the solid remnants is carried out after burning,directly in the wet separator.

The reheating of the pressure combustion products separated from dust tothe admission temperature of the gas turbine is carried out inaccordance with this invention so that the cooled and cleaned pressurecombustion products are Iirst carried over a heat exchanger, arranged inthe exhaust of the gas turbine, in which they are heated by the heat ofthe expanded driving gases, whereafter they pass over the alreadymentioned heat exchanger, arranged behind the pressure combustionchamber in the stream of the hot not cleaned pressure combustionproducts, by the heat of which they are heated to the admissiontemperature, at which they are thereafter brought as driving gases intothe gas turbine.

The steam-gas cycle has considerable requirements to the economicalregulation and operation. This pretentious requirement is met inaccordance with this invention so that the starting of the gas cycle andeventually also the regulation of the admission temperature of thedriving gases, i.e. of the cleaned and reheated pressure combustionproducts, is carried out by means of an auxiliary combustion chamber forHuid or gaseous fuel arranged in front of the gas turbine, into whichchamber compressed combustion air is supplied from a tap of thecompressor output and the combustion products of which are mixed withthe driving gases supplied to the gas turbine.

In the course of burning of solid fuel in the steam-gas cycle accordingto this invention, it is possible to supply prior prepared, i.e. driedand comminuted fuel from an auxiliary storage vessel to the stream ofcompressed pri-` mary air, with which it is brought into the pressurecombustion chamber.

At the elevated pressure of the combustion products in the combustionchamber and in the channels of the steamgas cycle it is also possible tocarry out the system according to this invention in combination with apressure circuit for the preparation, i.e. the drying and possibly alsothe disintegration of the fuel, where the fuel is dried and comminutedby the pressure combustion products or by the pressure combustion air.If pressure combustion products are used as drying medium, it ispossible to clean the drying medium from this circuit (the vapours) fromdust and use it together with the other pressure combustion productsafter reheating to the admission temperature for the drive of the gasturbine.

An example of an embodiment of the system according to this invention isshown schematically as a steam-gas arrangement in the accompanyingdrawing.

The compressor 1 driven by the gas turbine 6 sucks air from theatmosphere, compresses it and supplies it over the heat exchanger 4 tothe combustion chamber 2 of a steam generator 20, into whichsimultaneously solid fuel is supplied under pressure from a storage bin2l by a burner 22.

The pressure combustion chamber 2 for solid fuel is in this case a partof a steam generator, from which steam, generated by heat of thecombustion products, passes into the steam turbines 18 through a circuitof customary design, which is not shown in detail in the drawing, Thepressure combustion products generated in the combustion chamber 2containing solid remnants after combustion are cooled in a heatexchanger 3 for heating clean driving gases, in a heat exchanger 4 forheating combustion air and alternatively also in a heat exchanger 7provided as an auxiliary economiser for preheating water for the steamgenerator. In the stream of the not cleaned combustion products one ormore coolers can be provided, serving for other purposes of the circuitas for linstance for the regeneration of the solution for Washing outsulphur compounds and similar. In this case the further cooling of thecombustion products is carried out by water injection in a coolingchamber 9. The cooled pressure combustion products pass thereafterthrough a dust separator 5, Where they are at reduced temperatureseasily deprived of the solid remnants after combustion. A wet separatorcan be also used advantageously for this purpose. In this case a furthersaturator chamber 12 is provided behind the dust separator 5 where thecombustion products relieved of the dust are saturated by waterinjection. The combustion products cooled down and relieved of dust arethereafter heated in a heat exchanger 8 by the heat contained in theexpanded driving gases from the gas turbine 6 Whereafter they nally passthe already mentioned heat exchanger 3 Where the combustion productsrelieved of dust are again heated by hot combustion products stillcontaining dust to the admission temperature, at which they are fed tothe gas turbine 6. The gas turbine 6 drives the compressor 1 and thegenerator 11. The already mentioned heat exchanger 4 Where thecompressed combustion air is heated by means of compressed combustionproducts not yet relieved of dust, can be advantageously of theregenerating type.

From the tap of the output of the compressor 1 air is also supplied toan auxiliary combustion chamber 10 for fluid or gaseous fuel and thecombustion products from this chamber are mixed with the combustionproducts from the main combustion chamber 2 relieved of dust and heatedagain, with which they are supplied as driving gases to the gas turbine6.

It is self understood that the object of this invention in itsfundamental arrangement includes also other characteristic arrangementsof the steam-gas or gas circuits using the technology of preparation ofnot aggressive driving gases for a gas turbine from combustion productson the described fundamental principle.

An advantage of the described system of operation of the steam-gas, orgas circuit according to this invention is, that the lremoval of dustfrom the combustion products is carried out at low temperature, where incase a suitable dust cleaning device is used, a high degree ofcleanliness of the combustion products, required for the gas turbine,can be achieved. The heating of the pressure air by pressure combustionproducts is advantageous as at a relatively high specic weight of theair there is a good heat transmission coefficient. A regenerating heatexchanger is especially advantageous regarding price and operation. Thewell known drawback of the regenerating heat exchanger, that it is nottight does not matter as the penetration of air into the combustionproducts increases the surplus of air, it increases however the outputof the gas part of the steam-gas circuit, what is advantageous. Apossible pollution of the combustion air by the not cleaned combustionproducts is equally not damaging as the air is supplied into thecombustion chamber Where fuel with an ash content is burnt.

The cooling of the combustion products by water injection leads to anincrease of the output of the gas turbine and in a certain degreecontributes even to an increase of the efficiency of the wholearrangement. The combustion products relieved of dust are advantageouslyheated in recuperating heat exchangers in order to prevent a repeatedpollution. The heating takes place in a heat exchanger by combustionproducts from the gas turbine at normal pressure in order to reduce theloss of heat in the exhaust combustion products and furthermore bycombustion products not yet relieved of dust of high temperature. Thissecond heat exchanger must be made of a material which withstands hightemperatures, which is expensive. It is therefore advantageous, that theheated and cooled medium have high pressure, what influencesadvantageously the heat transmission coefficient and reduces the size ofthe heat exchanger.

The auxiliary combustion chamber for fluid or gaseous fuel enables aflexible start and regulation. It is necessary to supply to this chamberpressure air advantageously directly from the compressor and to mix thecombustion products from this chamber with the cleaned and heatedcombustion products supplied by the main combustion chamber. Thus thetemperature of the combustion products prior to their entrance into thegas turbine is lregulated.

It is advantageous to supply the comminuted solid fuel for a combinedsteam/ gas circuit or for a gas circuit from an auxiliary storage vesselinto the compressed primary air, with which it is brought into thepressure combustion chamber. This enables an independent operation ofthe fuel grinder and of the boiler without mutual influencing. The needof fuel for large energetic arrangements is large, what leads not onlyto the use v of large fuel grinders, but also to large cross sections ofall conduits and other devices of the grinder circuit. lt is thereforeadvantageous to choose a high pressure in the grinder circuit in orderto reduce the cross sections for the passage. The combustion productsused as drying medium in the grinder circuit (vapours) have to beperfectly relieved of dust and they can be thereafter supplied togetherwith the other combustion products into the gas turbine.

What we claim is:

1. A method of operating a gas turbine which cornprises:

(a) feeding a solid fuel and air under pressure higher than atmosphericpressure to a combustion zone;

(b) burning said fuel with said air in said zone,

whereby a hot gas of combustion having solid material suspended thereinis formed;

(c) cooling said gas and the suspended material to a lower temperature;

(d) separating the suspended material from the cooled sas;

(e) heating the separated gas first by heat exchange with an expandedgas and thereafter by heat exchange with said hot gas of combustion,whereby said hot gas of combustion is cooled to said lower temperature,said higher pressure being maintained during lsaid burning, saidcooling, said separating, and said heating; and

(f) expanding said heated gas in a gas turbine, Whereby said turbine isdriven, and the expanded gas for said heat exchange with said separatedgas is obtained.

2. A method as set forth in claim 1, wherein said gas and the suspendedmaterial are cooled by admixing water thereto.

3. A method as set forth in claim 1, wherein water is admixed to saidseparated gas prior to said expanding thereof. i,

4. A gas turbine arrangement comprising, in combination:

(a) a combustion chamber sealed from the atmosphere;

(b) irst feeding means for feeding a solid fuel to said chamber at apressure higher than atmospheric pressure;

(c) second feeding means for feeding air of combustion to said chamberunder said pressure for combustion of said fuel, whereby a hotcombustion gas under said pressure having solid material suspendedtherein is generated;

(d) heat exchanger means communicating with said chamber for receivingsaid hot combustion gas and the suspended solid material, said heatexchanger means being adapted to cool the received gas and Isolidmaterial to a lower temperature by heat exchange with another gas;

(e) separator means for separating said combustion gas from said solidmaterial;

(f) a irst conduit connecting said heat exchanger means with saidseparator means for conveying said gas and said solid material at saidlower temperature to 4said separator means;

(g) a second conduit connecting said separator means vwith said heatexchanger means for conveying the :separated combustion gas at saidlower temperature to said heat exchanger means for heat exchange withsaid hot combustion gas and solid material, whereby the hot combustiongas and solid material are cooled to said lower temperature, and saidseparated gas is heated to a higher temperature;

(h) a gas turbine;

(i) a third conduit connecting said heat exchanger means to said gasturbine for operating the same by the expansion of said heated.separated gas;

(j) additional heat exchanger means `arranged in said second conduit forpassage of said separated gas therethrough; and

(k) a third conduit connecting said additional heat exchanger means tosaid gas turbine for heat exchange of the expanded gas passing throughsaid additional heat exchanger means.

5. An arrangement as set forth in claim 4, wherein said A second conduitincludes saturator means for admixing Water to said separated gas.

6. A gas turbine arrangement comprising, in combination:

(a) a combustion chamber sealed from the atmosphere;

(b) feeding means for feeding a comminuted solid fuel to said chamber ata pressure higher than atmospheric pressure;

(c) an air compressor;

(d) a first heat exchanger communicating with said compressor and saidchamber for preheating air compressed by said compressor, and forfeeding the preheated compressed air to said chamber for combinationwith said fuel, whereby a hot gas of combustion carrying solid materialis formed;

(e) a second heat exchanger interposed between said chamber and saidfirst heat exchanger for cooling said gas of combustion and the carriedsolid material, and for transmitting the cooled gas of com- 6 bustionand solid material to said iirst heat exchanger for thereby preheatingsaid compressed air and further cooling said gas of combustion and solidmaterial;

(f) separator means communicating with said rst heat exchanger forseparating said further cooled gas from the solid material carriedthereby;

(g) a third heat exchanger interposed between said separator means andsaid second heat exchanger for reheating said separated gas in saidthird heat exchanger, and for heat exchange of the reheated separatedgas in said second heat exchanger with said hot gas of combustion andthe solid material carried, whereby said separated gas is furtherreheated and said hot gas of combustion and said solid material carriedthereby are cooled;

(h) a gas turbine connected to said third heat exchanger for receivingsaid further preheated gas, the expansion of said gas driving saidturbine;

(i) a conduit connecting said turbine to said third heat exchanger forconveying the expanded gas to said third heat exchanger, and for heatexchange between said expanded gas and 'said separated gas;

(j) motion transmitting means interposed between said turbine and saidcompressor; and

(k) power-consuming apparatus connected to said turbine.

7. An arrangement as set forth in claim 6, further comprising coolingmeans interposed between said rst heat exchanger and said separatormeans for additionally cooling said further cooled gas.

8. An arrangement as set forth in claim 7, wherein said cooling meansinclude means for admixing water to said further cooled gas.

9. An arrangement as set yforth in claim 6, further comprising saturatormeans interposed between said separator means and said third heatexchanger for admixing additional water to said separated gas.

10. An arrangement as set forth in claim 6, further comprising auxiliarycombustion means communicating with said turbine for burning a fuelsubstantially free from solid matter, whereby a fluid combustion productis formed, and for conveying said combustion product to said turbine.

References Cited by the Examiner UNITED STATES PATENTS 730,782 6/03Morrison 60-39.46 2,401,285 5 46 Woodward 6039.46 2,446,388 8/ 48Ramseyer 60--3 9.46 2,699,039 1/ 55 Yellott 60-39.46 3,002,347 10/ 61Sprague 60-39.46

FOREIGN PATENTS 999,019 9/ 51 France.

642,215 8/ 56 Great Britain.

663,398 9/51 Great Britain.

SAMUEL L. LEVINE, Primary Examiner.

1. A METHOD OF OPERATING A GAS TURBINE WHICH COMPRISES: (A) FEEDING ASLOID FUEL AND AIR UNDER PRESSURE HIGHER THAN ATMOSPHERIC PRESSURE TO ACOMBUSTION ZONE; (B) BURNING SAID FUEL WITH SAID AIR IN SAID ZONE,WHEREBY A HOT GAS OF COMBUSTION HAVING SOLID MATERIAL SUSPENDED THEREINIS FORMED; (C) COOLING SAID GAS AND THE SUSPENDED MATERIAL TO A LOWERTEMPREATURE; (D) SEPERATING THE SUSPENDED MATERIAL FROM THE COOLED (E)HEATING THE SEPARATED GAS FIRST BY HEAT EXCHANGE WITH AN EXPANDED GASAND THEREAFTER BY HEAT EXCHANGE WITH SAID HOT GAS OF COMBUSTION, WHEREBYSAID HOT GAS OF COMBUSTION IS COOLED TO SAID LOWER TEMPREATURE, SAIDHIGHER PRESSURE BEING MAINTAINIED DURING SAID BURNING, SAID COOLING,SAID SEPARATING, AND SAID HEATING; AND (F) EXPANDING SAID HEATED GAS INA GAS TURBINE, WHEREBY SAID TURBINE IS DRIVEN, AND THE EXPANDED GAS FORSAID HEAT EXCHANGE WITH SAID SEPERATED GAS IS OBTAINED.